SECIS元件

SECIS元件全称为硒半胱氨酸插入序列（SElenoCysteine Insertion Sequence），是生物mRNA中一个长约60nt的RNA元件，次级结构为一茎环^[1] ，此元件会使核糖体转译时不将UGA当作终止密码子，而将其作为编码特殊氨基酸硒半胱氨酸的密码子，因此为编码硒蛋白的mRNA所需。三域生物皆有SECIS元件^[2][3][4][5]，虽皆为茎环结构，但彼此序列差异很大（不过洛基古菌（英语：Lokiarchaeota）的SECIS元件序列和真核生物的较为接近）^[6]，细菌的SECIS元件通常紧跟在UGA密码子之后，真核生物与古菌的SECIS元件则位于mRNA的3'非转译区，可使mRNA中多于一个UGA密码子编码硒半胱氨酸，另外已知甲烷球菌属的一种古菌具有位于5'非转译区的SECIS元件^[7][8]。真核生物的SECIS元件通常有特殊的A：G碱基配对，可能对其功能相当重要^[9]。SECIS元件结合蛋白2（SECIS-binding protein 2，简称SBP2）可与SECIS元件结合以促进UGA密码子编码硒半胱氨酸^[10]，并可避免mRNA被无义介导的mRNA降解（NMD）途径降解移除^[11]。

SECIS元件
一个SECIS元件可能的次级结构，碱基标示为依循IUPAC规则
识别符
代号	SECIS_1
Alt.代号	SECIS
Rfam	RF00031
其他数据
RNA类型	顺式作用元件

目前已有数个生物资讯学软件可用于寻找基因组中的SECIS元件，有助于寻找新的硒蛋白^[12]。

12 sources

参考文献

• 分子与细胞生物学主题

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6. Mariotti, Marco; Lobanov, Alexei V.; Manta, Bruno; Santesmasses, Didac; Bofill, Andreu; Guigó, Roderic; Gabaldón, Toni; Gladyshev, Vadim N. Lokiarchaeota Marks the Transition between the Archaeal and Eukaryotic Selenocysteine Encoding Systems. Molecular Biology and Evolution. 2016, 33 (9): 2441–2453. ISSN 0737-4038. doi:10.1093/molbev/msw122.
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9. JULIA E. FLETCHER, PAUL R. COPELAND, DONNA M. DRISCOLL, ALAIN KROL. The selenocysteine incorporation machinery: Interactions between the SECIS RNA and the SECIS-binding protein SBP2 (PDF). RNA. 2001, 7: 1442-1453 [2021-05-23]. （原始内容存档 (PDF)于2021-05-23）.
10. Donovan J, Copeland PR. Selenocysteine insertion sequence binding protein 2L is implicated as a novel post-transcriptional regulator of selenoprotein expression.. PLoS One. 2012, 7 (4): e35581. PMC 3328465 . PMID 22530054. doi:10.1371/journal.pone.0035581.
11. Chellan B, Zhao L, Landeche M, Carmean CM, Dumitrescu AM, Sargis RM. Selenocysteine insertion sequence binding protein 2 (Sbp2) in the sex-specific regulation of selenoprotein gene expression in mouse pancreatic islets.. Sci Rep. 2020, 10 (1): 18568. PMC 7596060 . PMID 33122797. doi:10.1038/s41598-020-75595-4.
12. Lambert A, Lescure A, Gautheret D. A survey of metazoan selenocysteine insertion sequences. Biochimie. September 2002, 84 (9): 953–959. PMID 12458087. doi:10.1016/S0300-9084(02)01441-4.